The field of the present invention is the diagnosis of engine problems and, in particular, methods and devices for the diagnosis of fuel-related problems.
In many cases, an automobile brought in for servicing because of poor performance is not experiencing a mechanical problem, but rather a fuel problem. However, the diagnosis of fuel-related problems is often hampered by the lack of fuel analyzing equipment at the site of vehicle service. In addition, fuel-related problems can have diverse manifestations, including engine starting failures; engine performance difficulties such as engine hesitation, roughness and stalling after starting or upon de-acceleration around a curve; engine detonation difficulties; engine loss of power; poor engine fuel economy; engine missing and surging; noxious engine fumes; and smoky engine exhaust.
Determination of octane number and Reid vapor pressure are some of the most well known ways of characterizing a fuel. The octane number is a measure of a fuel's ability to resist engine knocking. Engine knocking results when a fuel fails to burn smoothly and evenly, and the resulting unburned portion of the air/fuel mixture explodes violently from spontaneous combustion. Octane number is conventionally determined and stated according to ASTM methods. For example, a research octane number (RON) can be determined according to ASTM Method 2699-84, and a motor octane number (MON) can be determined according to ASTM Method 2700-84. The conventional pump octane rating is determined as one-half the sum of RON plus MON.
Reid vapor pressure is a measure of a fuel's "front end volatility" or more volatile components. It can be measured by performing a "Reid Method" test procedure whereby a gasoline sample, which is sealed in a metal chamber, is submerged in a 100.degree. F. water bath. Higher readings are determined for the more volatile fuels because such components vaporize more readily, thus creating more pressure on the measurement device. Lower readings are determined for the less volatile fuels because such components create less vapor.
Various methods are known for the evaluation of octane number, Reid vapor pressure and other fuel properties. However, because these analytical tools are typically not available to automobile mechanics, there exists a need to provide a simple and relatively inexpensive method and device for quickly and reliably diagnosing fuel-related problems at the site of vehicle service.